From all the posts regarding "hijacking" presentations at Cocoa 2014 I get the idea that there must have been a lot of that or a particularly irritating individual. I wasn't at Cocoa this year, but have been to and have presented at a number of them. I have never had anyone behave badly in any of my presentations. I do not mind questions at any point if a member of the audience does not understand some point or if they have something pertinent to say.
